Audio Relay Delay | Electronic Project Circuits

Posts Tagged ‘audio relay delay’

Audio Amplifier Output Relay Delay

This is a simple circuit which I built to one of my audio amplifier projects to control the speaker output relay. The purpose of this circuit is to control the relay which turns on the speaker output relay in the audio amplifier. The idea of the circuit is wait around 5 seconds ofter the power up until the speakers are switched to the amplifier output to avoid annoying “thump” sound from the speakers. Another feature of this circuit is that is disconnects the speaker immediately when the power in the amplifier is cut off, so avoiding sometimes nasty sounds when you turn the equipments off.

Then power is applied to the power input of the circuit, the positive phase of AC voltage charges C1. Then C2 starts to charge slowly through R1. When the voltage in C2 rises, the emitter output voltage of Q1 rises together with voltage on C2. When the output voltage of Q2 is high enough (typically around 16..20V) the relay goes to on state and the relay witches connect the speakers to the amplifier output. It takes typically around 5 seconds after power up until the relay starts to conduct (at absolute time depends on the size of C2, relay voltage and circuit input voltage). When the power is switched off, C1 will loose it’s energy quite quickly. Also C2 will be charged quite quickly through R2. In less than 0.5 seconds the speakers are disconnected from the amplifier output.

Notes on the circuit:
This circuit is not the most accurate and elegant design, but it has worked nicely in my small home-built PA amplifier. This circuit can be also used in many other applications where a turn on delay of few seconds is needed. The delay time can be increased by using bigger C2 and decreased by using a smaller C2 value. Note that the delay is not very accurate because of simplicity of this circuit and large tolerance of typical electrolytic capacitors (can be -20%..+50% in some capacitors).
Author: Tomi Engdahl

Link: http://www.extremecircuits.net/2010/06/audio-amplifier-output-relay-delay.html

Be the first to comment - What do you think? Posted by admin - December 31, 2010 at 8:14 am

Categories: Electronic Control, Power Amplifier Tags: audio relay delay, delay speaker circuit

Hand Clap Electronic Control

We have all seen the commercial on TV ………. CLAP – ON – CLAP – OFF – THE – CLAPPER ………… well here is a circuit that will perform that same function.

Circuit operation is as follows. A single hand clap will be picked up by the electric mic which is coupled through C1 into the op amp IC1. The output of IC1 triggers the 555 IC timer IC2 which is configured as a monostable multivibrater. The trigger pulse is stretched by IC2 and outputs a pulse to IC3 a D type flip flop. Because of the three state counter arrangement of IC3, two sharp claps are required before IC3 will output a high to Q1 which will turn on K1 relay and any device connected to K1′s switch contacts. Two more claps will clock IC3 again and will turn off Q1 and any device connected to the K1′s contacts. I had my unit connected to my xmas tree lights so that I wouldn’t have to crawl behind the tree to turn the lights on and off. Sensitivity for the circuit is R3 and should be adjusted so that the circuit ignores normal room noise.

From :: http://home.maine.rr.com/randylinscott/dec97.htm